Sorry, you are wrong.
That was just 3 quick examples. These are not one off cards, there are thousands of cards of many different players in many different sports selling for this amount. Hundreds of thousands selling for $1k+.
There is more money in the sport card market now than ever before.
The 80s and 90s sportscards are basically all trash because of major over production. There are very few from this time frame that still hold value.
I agree the number of collectors is smaller now than the 80s/90s, but today's sports card market is doing just fine. No where near dead.
How many companies are producing baseball cards today? The next question, who are they catering to? How much does a pack of cards that may contain a $10K card cost?